The present invention relates generally to an adjustable twin axis steering column system for a vehicle, and more particularly to an adjustable twin axis steering wheel system for a vehicle that provides optimum safety for a driver in the event of a head-on collision.
It is known that injuries can occur in a head-on collision due to a so-called secondary collision of a vehicle occupant with a vehicle steering wheel. In order to prevent such a so-called secondary collision, a variety of steering column arrangements have been proposed and put into practical use. Such arrangements include a steering column structure, including a steering shaft, which contracted to absorb impact energy when a vehicle occupant collides against the steering wheel. This arrangement also included an airbag located inside a steering wheel, which was adapted to inflate so that the vehicle occupant would strike the inflated airbag, thereby absorbing any impact energy of the vehicle occupant if a head-on collision of the automotive vehicle occurs.
As is known, during a vehicle collision, it is usual that a driver seated on a driver""s seat will travel generally horizontally toward the front section of a vehicle body. It is also usual that the steering column is disposed such that it extends obliquely upwardly in a manner to incline relative to a front panel defining a passenger compartment.
The steering column, thus, extends along an axis that obliquely crosses the breast section of a driver. When a driver is thrown toward the vehicle body front section in a vehicle collision, the driver impacts the steering wheel and/or the airbag attached to the steering wheel. Accordingly, this secondary impact generates a component force in the axial direction of the steering column that contracts the column, and another perpendicular component force that attempts to push the steering wheel upwards perpendicular to the steering column. In view of the above, a structure for absorbing and attenuating the axial component force of the steering column in the secondary collision has been proposed and disclosed, for example, in Japanese utility model provisional publication nos. 60-81069 and 62-155067 in which a bellows type or resilient energy-absorbing body is interposed between the steering column and a front panel or dashboard.
However, drawbacks have been encountered in the above-discussed conventional steering systems, in which a space between the steering column and the front panel or the like is small, and therefore a sufficient stroke to absorb the horizontal component force at the secondary collision cannot be obtained even if the energy absorbing body is interposed in the space. Thus, in the conventional steering systems, an effective energy absorbing structure cannot be provided to protect a vehicle occupant upon the secondary collision.
A further attempt to solve the problem of the so-called secondary collision is disclosed in U.S. Pat. No. 5,503,431. The ""431 patent discloses a steering system having an upper shaft and a lower shaft. The lower shaft is axially movably connected to the upper shaft and includes a first section connected to the upper shaft, and a second section. The steering column has an upper bracket connected thereto. An energy-absorbing member is provided in a manner that the upper bracket is connected through the energy-absorbing member to a vehicle body to be generally horizontally movable relative thereto. A first universal joint is disposed between the first and second sections of the lower shaft. A bearing bracket is rotatably supported to the vehicle body and rotatably supports the second section of the lower shaft.
During a secondary collision where a vehicle occupant collides with a steering wheel, the impact load of the vehicle occupant is input to a column jacket through a steering wheel and the upper shaft. The impact force input to the column jacket is absorbed by the energy-absorbing member while the column jacket and the upper bracket horizontally move toward the front section of the vehicle body. Upon such a horizontal movement of the column jacket, the lower shaft horizontally moves thereby bending the first universal joint located at the upper side of the bearing bracket and allowing the bearing bracket to rotate. The system disclosed in the ""431 patent is extremely complicated, requires a multitude of parts, and is, thus, expensive to manufacture. The portion of the steering column that translates upon impact by the occupant""s torso includes the entire mass of the column jacket and the upper bracket. Reduction of the mass of the portion that translates forward reduces the potentially injurious impact force on the occupant""s torso.
It is an object of the present invention to provide an adjustable twin axis steering wheel system for a vehicle that provides optimum safety characteristics for a wide range of drivers having varying physical characteristics.
It is a further object of the present invention to provide an adjustable twin axis steering wheel system for use in a vehicle that utilizes a conventional steering shaft or steer-by-wire technology.
It is still another object of the present invention to provide a twin axis steering wheel system that orients the steering wheel to a favorable position in the event of a secondary collision.
It is still another object of the present invention to minimize the mass of the portion of the steering column that is translated forward in order to reduce the magnitude of potentially injurious force of impact upon the occupant""s torso.
In accordance with the above and the other objects of the present invention, an automatically adjustable twin axis steering wheel system is provided. The steering wheel system is part of a steer-by-wire steering system that allows the vehicle to be steered electronically. The steering wheel system includes a steering wheel pivotally attached to an upper subframe. The upper subframe is secured to a lower subframe, which is attached to the vehicle body structure by a translational joint. The translational joint allows the steering wheel system to be automatically adjusted to compensate for a driver""s stature. The upper subframe is moveable horizontally with respect to the lower subframe in the event of a driver exerting a sufficient force on the steering wheel.